Shock and acceleration resistant electron discharge device



Dec. 20, 1960 R. s. BRIGGS ET AL 2,965,791

SHOCK AND ACCELERATION RESISTANT ELECTRON DISCHARGE DEVICE Filed May 17,954 2 Sheets-Sheet 1 INVENTOR. RICHARD S. BRIGGS GEORGE E. CARTE JR.

ATTORNEY Dec. 20, 1960 R. s. BRIGGS ETAL 2,965,791

SHOCK AND ACCELERATION RESISTANT ELECTRON DISCHARGE DEVICE Filed May 17,1954 F l G. 4

2 Sheets-Sheet 2 F I G. 5

INVENTOR. RICHARD S. BRIGGS GEORGE E. CARTER R.

BY ATTORNEY States Patent O SHOCK ANDACCELERATION RESISTANT ELECTRONDISCHARGE DEVICE Richard S. Briggs, Beverly, and George E. Carter, Jr.,Danvers, Mass., assig'nors to Bomac Laboratories Inc., Beverly, Mass., acorporation of Massachusetts Filed May 17, 1954, Ser. No. 430,196

3 Claims. (Cl. 313-265) The present invention relates to electrondischarge devices and more particularly to a novel thermionic tube foruse under severe conditions of shock and acceleration and to a method ofassembling said tube.

Thermionic tubes having conventional electrode structure mounted withinan evacuated envelope cannot be employed in certain applications wherethe tubes and equipment are subjected to severe shocks andaccelerations. Prior art tube components and structure such as micaspacers, dielectric envelopes, electrode support struts, and weldedjoints are subject to breakage and distortion when employed in devicesoperated under such abnormal conditions.

Recent military developments have shown the increasing need forthermionic tubes capable of withstanding severe shocks and accelerationsup to 100,000 gravities. Further, the desired tubes must provideconventional tube characteristics.

It is an object of the present invention to provide a novel shock andacceleration resistant thermionic tube.

It is a further object to provide a novel shock and accelerationresistant thermionic tube having conventional tube characteristics.

A still further object is to provide rugged electrode support structurecapable of withstanding extreme shocks and high accelerations.

Another object is to provide a method of assembling an electrondischarge device of novel rugged structure.

The present invention discloses a thermionic device having metallicelectrode supports disposed at the ends of an envelope of a conductivemetal. The supports are assembled by utilizing glass to metal seals aswell as brazing techniques and the electrode structure is positionedwithin the envelope by means of the rigid support structure.

The objects, features, and advantages will be more readily appreciatedafter consideration of the following detailed description andaccompanying drawings in which:

Figure 1 is an enlarged perspective view of an illustrative embodimentof the present invention;

Figure 2 is a detailed cross-sectional view of the embodiment;

Figure 3 is a cross-sectional view along the line IIIIII in Figure 2;

Figure 4 is an exploded view in section showing the relationship of thecomponents of the present invention, exclusive of the cathode assembly;and

Figure 5 is an enlarged view of the cathode assembly.

Referring to the drawing, Figure 1 illustrates the construction of theenvelope of the embodiment of our invention. As shown, the envelopeconsists of cylindrical metallic members 1, 2, and 3, desirably of aconductive metal suitable for sealing to glass. Such a metal may beKovar, which consists of nickel, iron and cobalt, and has substantiallythe same coeflicient of expansion of a matching glass. Center member 2comprises the main body of the envelope and may be provided with ashoulder at each end, as at 4 and 5. In the final assembly of the2,965,791 Patented Dec. 20, 1960 2 tube according to the method of theinvention, cylindrical end members 1 and 3 are fitted on the shouldersof the center member and are sealed thereto to form a vacuum tightenclosure. The assembled envelope defines a central passageway in whichthe electrodes of the device are positioned.

End members 1 and 3 have sealed at their outer ends, cylindrical gridsupports 6 and 7 of a similar conductive metal having a smaller diameterthan said end members. A concentric glass bead 8 and 9 of a suitabledielectric material such as Corning 7052 or 707 glass maintains thepositioning of the grid supports coaxially with the end members 1 and 3.The point. of seal of the glass head is approximately, but not limitedto an intermediate point with the inwardly extending end rigidlysupporting the grid 10. Slots may be provided at the inner end of thegrid supports to allow for a snug engagement of the grid. In theembodiment of the invention, we have provided four slots, three of whichare visible in Figure 2 at 11, 12 and 13. If desired, the grid may bebrazed to the inner wall of the supports 6 and 7.

Grid 10 consists of a frame having parallel metallic side rods 15 and 16with a plurality of turns of a suitable wire helically wound and fixedthereon. The ends of the side rods have a substantial Y bend as at 17.The overall shape of the grid is generally rectangular as shown inFigure 3.

Cathode support members 18 and 19 of a still smaller diameter are nextsupported coaxially by grid supports 6 and 7. A glass bead 20 and 21positions the cathode supports in a similar manner to that previouslydescribed. Filamentary cathode 22 is firmly suspended within the centralpassageway by means of a spring bearing pin 38 and tubular member 23.One end of the filament may be swaged to the tubular member 23 as at 24.The other end is spring tensioned by means of a reverse coil spring 25attached to a mandrel section 26 on pin 38. The ends of spring 25 maybe: ai'fixed to the mandrel section by welding or brazing. Afterassembly of the filamentary cathode in the tube, the ends of the cathodemembers 18 and 19 may be sealed, as by soldering, as at points 27 and 28to provide a vacuum tight enclosure.

As shown in Figure 5, the filamentary cathode 22 is coated with asuitable emissive material 31 by the commonly employed methods such asspraying or cataphoretically coating said wire. In the illustrativeembodiment we have found the coating of barium and strontium carbonateswith a bonding agent produces the desired result with a tungsten wirefilament.

The concentricity and radial spacing of the electrodes will beappreciated in Figure 3. Outer envelope section 2 serves as the anode orplate electrode. Spaced within the central passageway defined by theenvelope and centered around a common axis are the cathode 22 and grid10 electrode. The latter two electrodes are rigidly supported to resistshock and acceleration by the tubular metallic members which alsoprovide good electrical conductivity. Since the selected metal Kovarpossesses the desired characteristics for sealing to glass, this metalhas been employed for all the supporting members, however, any othersuitable metal having similar characteristics for scaling to a matchingglass may be employed, if desired.

The advantages of the telescoping arrangement of all the metallicsupporting members will be appreciated in the ease of assembling andprocessing the tube of our invention.

Figure 4 shows the arrangement of the component parts in the method ofassembling the tube. Two end sub-assemblies are glass beaded to maintainthe parts in their desired relationship. Since both tube assembliespossess similar element spacings, a jig may be provided for thisoperation. The assembly of parts 3, 9, 7, 21, and 19 are next supportedin a suitable holding fixture in an upright position. Grid'ltl is thenfitted in the supporting member 7 and is rigidly held by the slottedsection.

Next, the center body member 2 is positioned on the assembly with asolder ring 32 resting against shoulder and the lip of this shoulderin-a snug relationship with the inner wall of the end member 3. Anothersolder ring 33 is fitted over shoulder 4 of said center body memberfollowed by the sub-assembly 1, 8, 6, 20, and 18. Grid engages the innerwall of the slotted support member 6. The dimensions of the assembledcomponents are selected to provide proper alignment of the electrodes.Hence, the shoulders 4 and 5 have dimensions which allow excellentelectrical continuity between members 1, 2, and 3, as well as a closefitted relationship at the ends of the grid 10 against support members 67'- Lastly, an exhaust tube 29, which is provided with a shoulder 35 anda solder ring 36 is inserted in a passageway 37 in the center body 2.

After assembly, the tube is fired or baked in an inert non-oxidizingatmosphere, such as hydrogen, to a temperature necessary to braze thejoined members. Such heat treatment serves to both clean the componentsas well as to braze the assembly. It will be evident that the danger ofcontamination of the cathode is avoided by providing this novelstructure and assembly. The brazed assembly is now ready 'for insertionof the cathode assembly.

A complete spring tensioned and coated filament cathode assembly ismounted -in the tube in an upright position with tubular member 23 beingintroduced through support member 18. Downward travel of the cathodeassembly will be terminated when the swaged portion 24 engages aninternally chamfered portion of member 19 as at 34. Tubular member 23 isthen secured to the cathode support member 19 by soldering.

With one end of the cathode securely positioned, tension may be placedon the pin 38. We have provided the pin 38 with a longer overalldimension to facilitate the tensioning operation. As soon as the desiredtension has been attained, pin 38 may be cut and similarly soldered tosupport member 18.

The tube is next evacuated and gettered by known techniques and exhausttube 29 tipped and sealed as at 30.

External electrical connections for the components may be made in asimple and efficient manner. The grid electrode supports 6 and 7 furnishmeans for attaching lead wires to energize the grid and similarconnecting wires may be attached to tubular members 18 and 19 toenergize the cathode electrode. Since the outer envelope section 2 formsthe anode electrode, a lead wire may be similarly attached to thissection.

Other forms of electrical connections, such as a elamping device havingelectrically conductive tabs may also be employed.

The embodiment of our invention may be further strengthened by securingthe suitable lead wires and then immersing the tube in a rubber orplastic coating compound to cover all exterior surfaces.

Tubes of the character described have performed satisfactorily as anoscillator with warm-up times of under three-tenths of a second. Withsuitable circuitry the tube may also be adapted to function as anamplifier, rectifier or detector tube.

Due to the compactness of the structure the device disclosed also lendsitself quite readily to modern high speed production methods.

While we have described an illustrative embodiment of the invention,various modifications of the structure or method may occur to thoseskilled in the art. It is, therefore, our intention to cover in theappended claims such modifications or variations as fall within thespirit and scope of the invention.

What is claimed is:

1. A shock and acceleration resistant thermionic tube comprising acylindrical anode electrode, a first pair of tubular electrode supportssealed at the ends thereof by means of a dielectric material, a gridelectrode extending axially between said supports, a second pair oftubular electrode supports sealed at the ends of said first pair ofsupports by means of a dielectric material, a cathode electrodeextending axially between said supports, said first and second pair ofelectrode supports being in telescoping arrangement and said electrodesbeing disposed eoncentrically around a common axis with the ends or eachof said electrodes in contiguous'relationship'with said electrodesupports. I

2. .An electron discharge device comprising a cylindrical'envelope of acondu ctive metal, said envelope 'defining a central passageway therein,a plurality of metallic tubular electrode support members disposed ateach end of said passageway, said metallic tubular support members beingdisposed in axial alignment and supported radially one from the other intelescoping arrangement by means of a dielectric seal therebetween, saiddielectric seals being disposed at the ends of each of said tubularsupport members, said tubular support members having in contiguousrelationship therebetween a grid electrode and filamentary cathodeelectrode assembly, said grid electrode. and cathode electrodeassemblies being disposed concentrically within said central passagewayaround a common axis with each electrode being supported at opposed endsby said tubular support members. v

3. electron discharge device comprising a cylindrical envelope having acenter metallic body section and a metallic tubular section disposed ateach "end thereof, said envelope defining a central passageway, a firstpair of metallic tubular-electrode supports of smaller diameter axiallyand oppositely disposed at each end of said central passageway, saidsupports being joined by means of a. dielectric material to the ends ofsaid'tubular sections, a grid electrode-extending axially between theinner ends of said first pair of tubular supports, a second pair ofmetaliictubular electrode supports of still smaller diameter joined bymeans of a dielectric material to 'the ends of said first parrot tubularsupports, said second pair of tubular supports defining wall structurepermitting access to the central'passageway, a filamentary cathodeassembly extending axially through said central pass'ageway with thesupporting members of said cathode assembly engaging the inner walls ofsaid second pair of tubular electrode supports.

References Cited in the file of this patent UNITED STATESPATENTS1,709,029 Little Apr. 16, 1929 2,128,231 Dalleilb aeh Aug. 30, 19382,478,969 Ishler Aug. 16, 1949 2,509,906 Clark et al. May 30, 19502,521,315 Victoreen Sept. .5, 1950

